The present invention concerns integrated circuit devices comprising an active layer and an additional layer fixed to one active face of said active layer. The present invention further concerns cards provided with these devices, sections of a semiconducting material provided with a plurality of these devices, as well as methods for producing these devices.
The above-mentioned integrated circuit devices are specifically described in the international applications published under the numbers WO-96/16378, WO-97/11442 and WO-99/12204. Other devices are described in the patent applications filed in France under the numbers FR-98/081305, FR-98/13029 and FR-99/00858 which have not been made available to the public on the date of priority of the present application.
These devices are intended to process or store confidential data so as to carrying out, for example, electronic transactions in the various fields, such as those concerning health, pre-paid television, telephone applications or banking.
To this effect, the devices include volatile and non-volatile memories of the ROM, RAM, EEPROM, Flash PROM or Ferromagnetic RAM type, as well as a central processing unit or CPU, which manages and distributes said confidential data by means of address and data buses.
In practice, the devices are integrated inside an electronic module and mounted inside a card body as defined in the standards ISO 7816 and 14443 or GSM 11.11 and 11.14. Moreover, contact blocks of the devices are connected to contact areas flush with the surface of the card body, or else to the contact terminals of an antenna embedded in the card body, which enables the cards to communicate with the outside world. Depending on their mode of operation, the cards are known as contact, non-contact or mixed cards.
By means of the devices of the invention, the protection of data stored or processed in the cards is improved. In fact, physical attacks tending to disassociate the additional layer and the active layer to obtain a non-destructive access to the integrated circuit are no longer possible. The same applies for certain embodiments of said devices concerning attacks known as attacks in light in which a focussed electromagnetic radiation disturbs the protective functioning of the chip.
However, other attacks may be used with some success against known devices. These are physical attacks carried out by the controlled destruction of the additional layer and in particular attacks by polishing or etching said layer. Owing to these attacks, fraudulent persons could. access the active face of an integrated circuit device without damaging said circuit, and then learn about the architecture of the circuit and possibly implement the previously prohibited attacks, such as attacks in light, so as to access the confidential data.
In the case of attacks by polishing, a rotating polishing plate is brought parallel to the plane of the additional layer. This plate erodes this layer in a controlled way until the level of the active face is reached.
In attacks by etching, various known methods can be implemented. This is in particular the case with the RIE method (Reactive Ion Etching) which is carried out by a dry process. According to this method, reactive chemical compound preparations are created inside an electrically neutral plasma then absorbed on the surface of the additional layer of a device where they form a molecular layer of chemical complexes. Ions highly accelerated in an electrostatic field are then directed perpendicular to the additional layer of the device and destroy the molecular chemical complex layer. The additional layer, or more specifically a portion of this layer, not including the openings intended to allow an electric connection to the contact blocks, is thus finally destroyed layer by layer up to the level of the active face.
Having regard to the foregoing, the invention seeks to resolve one particular problem, namely to protect the integrated circuit devices comprising one active layer including a semiconducting material, a circuit integrated with one active face of said active layer, said integrated circuit comprising circuit elements and at least one contact block flush with said active face, and an additional layer fixed to said active face, said additional layer covering at least partially said integrated circuit of said active face against attacks via a controlled destruction of said additional face.
With regard to the above-mentioned problem, the solution of the invention aims to provide a device characterised in that a hole is provided in the additional layer, said hole being situated plumb with at least one circuit element.
Thus, destruction of the additional layer can no longer be controlled and the circuit element situated plumb with the hole is destroyed.
In addition, the object of the invention is also to produce a card body equipped with a device conforming to the invention, a section of a semiconducting material fitted with a plurality of devices according to the invention, as well as a method for producing said device.
The following description, which is in no way restrictive, shall make it possible to understand how the invention can be put into practice. This description is given with reference to the accompanying drawings on which: